In a large number of electronic control devices, semiconductive components are placed having with a restricted surface with respect to the surface of the element supporting them. This is thus the case with, for example, active matrix flat display screens where each image element of the screen (or pixel) is controlled by a transistor. The techniques currently employed for this type of device use hydrogenated amorphous silicon or polycrystalline silicon for the production of transistors to control the pixels.
During the production of these transistors, the entire surface of the support on which the pixels are shaped is covered with a film of an amorphous semiconductive or, depending on the case, a polycrystalline material. Then the largest portion of this film is etched so as to only leave the zones reserved for the transistors. The surface occupied by the control transistors merely represents a small portion of the surface of the pixel (less than 20%). An effort is being made to reduce this parasitic occupation and those of interconnections so that the luminous transmission loss of the screen is minimal.
This traditional method for producing pixel control transistors thus provokes the dissipation of the major part of the initially placed silicon film. Up until now, a lot of importance has not been attached to this occurence because the cost of placing of an amorphous silicon or polycrystalline film is low. This is no longer the case if it is desired to use a superior quality semiconductive material and in particular monocrystalline silicon. This case of dissipating the major part of the silicon film thus constitutes a serious drawback.